Well workable, abrasion resistant nodular cast iron and a method of its production

ABSTRACT

A nodular cast iron, said cast iron containing in its soft ferrite matrix (Brinelle hardness about 180 kg/sq.mm) spherulites of nodular graphite, said graphite playing the role of lubricant for machine elements cooperating together in friction, and very hard spherulites of a eutectic and hypereutectic alloy cementite (Brinelle hardness about 800 kg/sq.mm) and having the following composition: 2.6 TO 2.8 % C; 4.0 to 4.5 % Si; 0.1 to 0.2 % Mn; 0.15 to 0.25 % Cr; 0.03 to 0.06 % S; and 0.05 to 0.08 % P. The nodular cast iron may be produced by melting a metal charge consisting of low-manganese pig iron, scrap steel, scrap iron, and ferro-alloys in an induction furnace, and after obtaining the composition: 2.7 TO 2.9 % C; 2.4 to 2.9 % Si; 0.1 to 0.2 % Mn; 0.10 to 0.20 % Cr; 0.07 % S; and 0.06 % P, spheroidizing after the addition of a ferrosilicomagnesium master alloy in a quantity of 2.5 to 3.0 % based on the weight of the cast iron, said master alloy containing on an average 45 % Si and 8 % Mg. To obtain the composition according to the invention the ferrosilicon and ferro-chromium are added to the casting ladle after the spheroidizing treatment.

United States Patent 1 Gierek et al.

[ Nov. 18', 1975 [73] Assignee: Politechnika Slaska Im. Wincentega Pstrowskiego, Gliwice, Poland [22] Filed: Feb. 15, 1974 [21] Appl. No.: 443,039

[30] Foreign Application Priority Data Apr. 27, 1973 Poland 162215 [52] US. Cl 75/130 R; 75/126; 75/130 A [51] Int. Cl C22c 33/00; C22c 39/14 [58] Field of Search 75/126, 130

' [56] References Cited UNITED STATES PATENTS 2,761,801 9/1956 Armstrong 75/126 Q 3.113.019 12/1963 Adams 3.591366 7/1971 Triches 3,744,998 7/1973 Loricchio 75/130 R Primary E.\'aminerP. D. Rosenberg Attorney, Agent, or Firm-Haseltine, Lake & Waters [57] ABSTRACT A nodular cast iron, said cast iron containing in its soft ferrite matrix (Brinelle hardness about 180 kg/sq.mm) spherulites of nodular graphite, said graphite playing the role of lubricant for machine elements cooperating together in friction, and very hard spherulites of a eutectic and hypereutectic alloy cementite (Brinelle hardness about 800 kg/sq.mm) and having the following composition;

2.6 to 2.8 C; 4.0 to 4.5 Si; 0.1 to 0.2 Mn; 0.15 to 0.25 Cr; 0.03 to 0.06 S; and 0.05 to 0.08 P.

The nodular cast iron may be produced by melting a metal charge consisting of low-manganese pig iron, scrap steel, scrap iron, and ferro-alloys in an induction furnace, and after obtaining the composition:

2.7 to 2.9 C; 2.4 to 2.9 Si; 0.1 to 0.2 Mn;

0.10 to 0.20 Cr; 0.07 S; and 0.06 P,

spheroidizing after the addition of a ferrosilicomagnesium master alloy in a quantity of 2.5 to 3.0 based on the weight of the cast iron, said master alloy containing on an average 45 Si and 8 Mg.

To obtain the composition according to the invention the ferro-silicon and ferro-chromium are added to the casting ladle after the spheroidizing treatment.

5 Claims, No Drawings WELL WORKABLE, BRAs ON RESISTANT NODULAR CAST IRON AND A METHOD OF ITs PRODUCTION BACKGROUND OF THE INVENTION pared with the carbon content in the cast iron, according to the invention results from carbon content reduction by 0.1 to 0.2 during spheroidizing treatment.

According to a modified version of the method ac- 5 cording to the invention, the metal charge consisting The invention relates to an easily machinable abracharacteristic for a perlitic cast iron, or a high abrasion resistance, hardness and brittleness, which are characteristic of cast irons having a perlite-ledeburitic matrix.

Nevertheless, the application of ledeburitic cast irons in industrial practice is limited because of the high brittleness and hardness of these irons. Because of these acute imperfections cast irons of this type hardly lend themselves to machining. This limitation leads to substituting of abrasion'resistant ledeburitic cast irons by the more expensive but, at the same time, more plastic alloys of non-ferrous metals and alloy steels.

SUMMARY OF THE INVENTION The object of the present invention is to obtain a nodular cast iron of a new type, this cast iron possessing a high abrasion resistance and lending itself very well to machining.

This object has been attained by developing and producing a nodular cast iron which in its soft ferritic matrix (Brinelle hardness about 180 kg/sq.mm) contains spherulites of nodular graphite, this graphite playing ,the role of a lubricant for cooperating elements in a machine, and very hard spherulites of eutectic and hypereutectic alloy cementite (Brinelle hardness about 800 kg/sq. mm) the'latter spherulites improving abrasive resistance, the permissible trace of perlite content in the structure being about 3 percent.

DESCRIPTION OF PREFERRED EMBODIMENTS The composition of the nodular cast iron according to the invention is as follows:

2.6'to 2.8 C; 4.0 to 4.5 Si; 0.l to 0.2 Mn; 0.15 to 0.25 Cr; 0.03 to 0.06 S; and 0.05 to 0.08 P. The method of producing the nodular cast iron consists of melting the metal charge consisting of low-manganese pig iron, scrap iron, scrap steel and ferro-alloys in an induction furnace, so that after the fusion takes place the cast iron has the following composition:

2.7. to 2.9 C; 2.4 to 2.9 Si; 0.1 to 0.2 Mn; 0.10

to 0.20 Cr; about 0.07 S; and 0.06 P. Next, a spheroidizing treatment is carried out after the addition of a ferrosilicomagnesium FeSiMg master alloy in a quantity of 2.5 to 3.0 based the weight of cast iron subjected to spheroidizing, the master alloy containing 40 to 50 Si, 6 to 8 Mg, the balance being iron. The silicon content in the cast'iron is complemented by adding the ferrosilicomagnesium master alloy during the spheroidizing treatment, and the content of chromium up to value of 0. to 0.25 is complemented after spheroidizing treatment by adding ferro-chromium which contains 60 Cr, and then the iron is cast directly into the casting molds. A higher content of carbon in the cast iron after melting, as commainly of low-manganese pig iron containing on an average 3.9 C, 1.7 Si, 0.005 Mn, and 0.01 Cr, is melted in an electric furnace, particularly in an arc furnace together withthe'fei'ro-alloy additions, such as: ferro-silicon, ferro-chromium, and ferro-manganese, in such quantities that after melting the following composition is obtained: v

2.7 to 2.9 C, 2.4 to 2.9 Si, 0.1 to 0.2 Mn, 0.10

to 0.20 Cr, 0.07 S, and 0.07 P.

A reduction in carbon content to the value specified in the invention is obtained by intensive burning out of carbon in an arc furnace.

The cast iron according to the invention has an improved abrasive resistance, while its high strength properties are retained. Besides, a characteristic quality of the cast iron according to the invention is its good plasticity which permits cooperative elements made of this cast iron to readily adjust to each other. This quality additionally causes the cast iron to lend itself very well EXAMPLE 1.

Metal charge composition (per ton of cast iron):

- low-manganese pig iron (4.3 C; 0.17 Si; 0.005

% Mn; 0.01 Cr) 600 kg scrap steel (0.3 C; 0.5 Si; 0.7 Mn; 0.07 S;

0.06 P) 200 kg scrap iron (2.8 of C; 4.0 Si; 0.2 Mn; 0.07

S; 0.06 P) 100 kg.

- ferro-silicon Si) 30 kg ferro-chromium (60 Cr) 35 kg Melting in an induction furnace.

Composition after melting: 2.7 to 2.9 C; 2.4 to 2.9 Si; 01 to 0.2 Mn; 0.1 to 0.2 Cr; 0.08 S; and 0.06 P.

spheroidizing temperature 1460C Quantity of ferrosilicomagnesium master alloy (45 Si; 8 Mg) kg Additives added into the casting ladle after spheroidizing treatment:

- ferro-chromium (60 Cr) 1.5 kg

- ferro-silicon (75 Si) 1.5 kg

EXAMPLE 2 Metal charge composition (per ton of cast iron) low-manganese pig iron (3.9 C; 1.7 Si; 0.005

Mn; 0.01 cr) 974 kg.

- ferro-manganese Mn) 2.25 kg ferro-chromiun (60 Cr) 3.50 kg ferro-silicon (75 Si) 20 kg Melting in an induction furnace.

Composition after melting:

2.7 to 2.9 C; 2.4 to 2.9 Si; 0.1 to 0.2 Mn;

0.1 to 0.2 Cr; 0.07 S; and 0.06 P.

Quantity of ferrosilicomanganese master alloy (45 Si; 8 Mg) 30 kg.

Additives added into the casting ladle after spherodizing treatment:

- ferro-chromium (60 Cr) 1.5 kg

3 ferro-silicon (175 Si) 1.5 kg We claim: 1. An easily machinable, abrasion resistant nodular cast iron consisting of 2.6 to 2.8 C; 4.0 to 4.5 Si; 0.1 to 0.2 Mn; 0.15 to 0.25 Cr; 0.03 to 0.06 S; 0.05 to 0.08 P,

the balance being iron, said cast iron having a structure consistingof a metal matrix in the form of silicon ferrite, nodular spherulites of graphite, and carbon bonded in the form of eutectic and hypereutectic alloy cementite, the perlite content in the structure being not more than about 3 2. A method for producing the nodular cast iron as claimed in claim 1, comprising melting a metal charge consisting of low manganese pig iron, scrap steel, scrap iron, ferro-silicon, and ferro-chromium, in an induction furnace, said charge containing after melting:

2.7 to 2.9 C; 2.4 to 2.9 Si; 0.] to 0.2 Mn; 0.10

to 0.20 Cr; about 0.07 S; and 0.06 P,

the balance being iron; adding a ferro-silicomagnesium master alloy in an amount of 2.5 to 3.0 based on the weight of liquid cast iron, said master alloy containing on an average 45 Si, and 8 Mg, and spheroidizing to bring the silicon content up to 4.0 to 4.5 and adding ferro-chromium,

4 said ferro-chromium containing about 60 Cr. to bring the chromium content up to 0.15 to 0.25%. 3. A method for producing the nodular cast iron as claimed in claim 1 comprising melting a metal charge consisting of low-manganese pig iron, said pig iron containing on an average 3.9 C; 1.7 Si; 0.005 Mn, and 0.01 Cr, in an arc furnace, together with ferroalloys, added in such quantities that after melting the cast iron has the following composition:

2.7 to 2.9 C; 2.4 to 2.9 Si; 0.1 to 0.2 Mn; 0.1

to 0.2 Cr; 0.07 S; and 0.07 P, adding a ferrosilicomagnesium master alloy in a quantity of 2.5 to 3.0 based on the weight of cast iron, said master alloy containing on an average 45 Si, and 8 Mg, and spheroidizing to bring the silicon content up to 4.0 to 4.5 and adding ferrochromium, said ferro-chromium containing about 60 Cr, to bring the chromium content up to 0.15 to 0.25 4. A method according to claim 2 wherein the spheroidizing temperature is 1460C.

5. A method according to claim 3 wherein the spheroidizing temperature is 1460C.

l l =l 

1. AN EASILY MACHINABLE, ABRASION RESISTANT NODULAR CASTIRON CONSISTING OF 2.6 TO 2.8%C; 4.0% TO 4.5%SI; 0.1 TO 0.2% MN; 0.15 TO 0.25 % CR; 0.03 TO 0.06% S; 0.05 TO 0.08% P, THE BALANCE BEING IRON, SAID CAST IRON HAING A STRUCTURE CONSISTING OF A METAL MATRIX IN THE FORM OF SILICON FERRITE. NODULAR SPHERULITIES OF GRAPHITE, AND CARBON BONDED IN THE FORM OF EUTECTIC AND HYPEREUTECITIC ALLOY CEMENTITE, THE PERLITE CONTENT IN THE STRUCTURE BEING NOT MORE THAN ABOUT 3%.
 2. A method for producing the nodular cast iron as claimed in claim 1, comprising melting a metal charge consisting of low manganese pig iron, scrap steel, scrap iron, ferro-silicon, and ferro-chromium, in an induction furnace, said charge containing after melting: 2.7 to 2.9 % C; 2.4 to 2.9 % Si; 0.1 to 0.2 % Mn; 0.10 to 0.20 % Cr; about 0.07 % S; and 0.06 % P, the balance being iron; adding a ferro-silicomagnesium master alloy in an amount of 2.5 to 3.0 % based on the weight of liquid cast iron, said master alloy containing on an average 45 % Si, and 8 % Mg, and spheroidizing to bring the silicon content up to 4.0 to 4.5 %; and adding ferro-chromium, said ferro-chromium containing about 60 % Cr, to bring the chromium content up to 0.15 to 0.25%.
 3. A method for producing the nodular cast iron as claimed in claim 1 comprising melting a metal charge consisting of low-manganese pig iron, said pig iron containing on an average 3.9 % C; 1.7 % Si; 0.005 % Mn, and 0.01 % Cr, in an arc furnace, together with ferro-alloys, added in such quantities that after melting the cast iron has the following composition: 2.7 to 2.9 % C; 2.4 to 2.9 % Si; 0.1 to 0.2 % Mn; 0.1 to 0.2 % Cr; 0.07 % S; and 0.07 % P, adding a ferrosilicomagnesium master alloy in a quantity of 2.5 to 3.0 % based on the weight of cast iron, said master alloy containing on an average 45 % Si, and 8 % Mg, and spheroidizing to bring the silicon content up to 4.0 to 4.5 %; and adding ferro-chromium, said ferro-chromium containing about 60 % Cr, to bring the chromium content up to 0.15 to 0.25 %.
 4. A method according to claim 2 wherein the spheroidizing temperature is 1460*C.
 5. A method according to claim 3 wherein the spheroidizing temperature is 1460*C. 